Device for interrupting the power supply to an object

ABSTRACT

A device is provided for interrupting the power supply to an object and is characterized in that it has elements (1, 2, 11) for effecting at which time the power supply shall be interrupted. The device is particularly adapted for use in connection to electrical stoves, as its function is such that accidents occurring because of overheating of stove plates or setting of fire to foodstuffs and the like used in connection to use of the stove can be avoided, and an obvious advantage in comparison to conventional stoves is thus obtained.

FIELD OF THE INVENTION AND PRIOR ART

This invention relates to a device for interrupting the power supply toan object, particularly after a certain operation time or after an alarmfrom any device associated with the present device and adapted to thistarget. Stoves are here treated as an example of such an object, thestoves forming arrangements by which it is possible to substantiallyreduce the risks by means of a device according to the present inventionfor such accidents that have occurred at a large number of occasions asstove plates have been overheated or as objects located on the stoveplate has caught fire due to the heat thereof.

Investigations show that a large number of accidents occur throughoverheated objects being set on fire. Accordingly, by way of example,30% of all the fires in homes are caused by electrical stoves, i.e.because of the user having forgotten to turn off the stove. Also inthose cases where such negligence does not cause fire, other economicaldamage is obtained, such as damaged hot plates and/or cooking vesselsdue to excessive heating.

Due to similar reasons, and to avoid wasting energy in vain, it is alsoan advantage to be able to control the power supply to an oven includedin a stove so that the power supply is interrupted after a certainoperation time or at a given alarm signal from any alarm deviceassociated with the oven.

It is known per se to arrange means or arrangement for interrupting thepower supply to objects heated by means of the power supply and therebyrunning the risk of being overheated. However, such means orarrangements have the disadvantage of having only a thermostat functionand will turn the power supply off only on the basis of the temperatureof the object in question. Then, as the temperature is under a certainvalue, they will once again make the power supply possible. Anypermanent interruption of the power supply to the object when the latterhas been used for certain time or reached the temperature which is toohigh will not be effected by these devices of prior art.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device forinterrupting the power supply to an object, particularly a stove, andmore precisely the hot plates or the oven thereof, to obtain advantagesin comparison to stoves of a conventional type with reference to safetyaspects and economical aspects, regard being taken to the elapsed timeat every occasion when the object is used.

Therefore, the device according to the invention comprises means foreffecting at which time, that is to control when, the power supply is tobe interrupted.

In a preferred embodiment of the invention, these means comprise a timerwith which a desired operation time of the object can be set.

According to another preferred embodiment, the object itself has one ormore own power supply breakers, which as in the case of stoves, cancomprise knobs which are maneuvered by hand by the one handling theobject. They may comprise breakers associated to possible thermostatfunctions of the object in question. If the user of the object wouldforget to turn the power supply off through the object's own breakers,the device will, accordingly, effect the accomplishment thereof as a setoperation time has passed or, as will be explained hereinafter, after acertain number of on- and off-switching cycles regarding the powersupply to the object has occurred or an alarm signal has been given tothe device.

According to yet another preferred embodiment, the device also comprisesmeans for keeping the power supply to the object interrupted until theobject's own breakers are open. Thereby, particularly breakersmaneuverable by hand are referred to, such as a those associated toknobs present at stoves. An advantage obtained through thischaracteristic is that the user thereby has to actively open the powersupply breakers of the object before power once again can be supplied tothe object. Of course, this reduces the risks for possible accidents.

According to another preferred embodiment of the device according to theinvention, this one comprises means which only at a period ofinterruption of the power supply to the object that exceeds apredetermined value will reset the timer to once again start from zero,that is from the beginning, during its measure of the operation time.Power supply interruptions that are controlled by thermostat or causedby the user and the length of which is such that it goes below theabove, predetermined time period, will not effect the timer's countingof the operation time. Thus, in the case with stoves, the user can turnthe power supply of the stove off for a shorter period without therebyresetting the timer, which is an advantage in certain situations.

In another preferred embodiment, the devices are provided with means fordetecting whether the object's own power supply breakers are closed ornot. Thereby a condition is created for certain other functionsaccomplishable by the device in different embodiments.

Accordingly, the device according to yet another embodiment is alsocharacterized in that it comprises means which, as the power supply tothe object has been interrupted by the device, make the means fordetecting whether the object's own breakers are closed or not to executeit's detecting function with a time period which, between the detectingfunction occasions, step-wise becomes longer. Every time such adetection is made, the object is supplied with a small amount of power.If this is done regularly and with pauses that are too short, the objectremains at an unacceptably high temperature if it, by way of example, isa stove plate which is supplied with current. With this embodiment, thisproblem is solved as the periods of the pauses initially are short butthen successively becomes longer. In that way, it is possible to obtainbody temperature as final temperature also for a high effect stove plateset at maximum effect.

According to another characteristic, the device comprises meanseffecting the maintenance of the time period between the detectingfunction occasions at a predetermined, maximum value after said timeperiod having been increased to this value. For a stove plate typicallyaround one minute. Thereby, the power supply to the object can rapidlybe regained after the power supply breakers of the object having beenre-opened, e.g. after the knobs having been reset, because the device,when having determined that this is the case by means of the detectingmeans, re-closes it's own breakers.

According to another embodiment of the device according to the inventionit also comprises a means effecting the interruption of the power supplyto the object as the power supply has been switched on and offrespectively a predetermined number of times by the object's ownbreakers without the timer having been allowed to reach the end of theoperation time. According to yet an embodiment this means is connectablyand deconnectably arranged and is connected depending on which part ofthe object that is supplied with power. In the case of a stove, thispart of the object, that is the stove, is preferably constituted by theoven, as the thermostat function of ovens normally is such that theinterruption periods as to power supply are of such length that a timerfunction, as described above, time after time would reset the timer.Thus, this problem is remedied through these characteristics.

BRIEF DESCRIPTION OF THE DRAWING

Further advantages and characteristics of the device according to thepresent invention will appear from the following description in detailof a preferred embodiment, made with reference to the disclosed drawing,which shows a block diagram for the device according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The figure shows the different units which make part of the deviceaccording to the invention, the object supplied with power, here bymeans of three phase feeding, being formed by a stove, preferably anelectrical stove. Preferably, also the device according to the inventionis driven by power from the same source as the one of the object.

To handle the signalling between these units, the device comprises acontrol unit 1 which here is formed by a micro controller with acomputer program adapted to the handling of signals.

Here, the means, as described above, for effecting the time when thepower supply to an object is to be interrupted comprises a timer 2 whichpicks up an operation time from a block 4 for time setting as a signalis given from the control unit 1 via a conductor 3 to itsstart-timer-inlet, and counts this period down to zero. Simultaneouslywith the pick-up of operation time the output of said means are set tozero. When the period or time has been count down to zero a signal isgiven to the control unit via a conduct 5. Furthermore, via anotherconduct 6, a signal is given to the control unit already when apredetermined time remains of the set period. When this predeterminedtime remains of the operation time, the device determines whether powersupply to the object is taking place by means of detecting means whichwill be further described later. If the device finds that there is nopower supply to the object at this occasion, it waits for such a supplyto occur and then, as soon as this occurs, interrupts the power supplyby means of it's breakers 11. Therefore, the time of use can at minimumbe operation time minus a predetermined time, and at maximum be theoperation time.

In the preferred embodiment, the setting of the operation time iseffected by choosing an on-position or off-position at the threeswitches 7, which results in eight different combination possibilities.One of the possibilities, here in the case when all switches are intheir off-position, is that no time is to control the device. Then, asignal is given from the time setting block 4 via a conduct 8 to thecontrol unit 1. The remaining combination possibilities give differentoperation times which, via conducts 9, is picked up by the timer.

The device is also provided with a counting means 10 which effects thatthe power supply to the object is interrupted by the device as the powersupply to the object has been switched on and interrupted apredetermined number of times through the object's own breakers withoutthe timer 2 having been permitted to reach the end of the operationtime. In the block diagram this counting means is illustrated by theblock 10, and is, via a conduct, directly connected to a means 13 fordetecting whether the own power supply breakers of the object suppliedwith power are closed or not. Via conducts 14, 15 this means is alsoconnected to the control unit and can be switched on or off by means ofa switch 16 depending on which part of the object that is supplied withpower. In the preferred embodiment, the part supplied with power whenthe counting means is supposed to be switched on is the oven of a stove.

In the preferred embodiment, the detecting means comprise a unitrepresented by means of a block 13. Preferably this unit comprises meansfor measuring if the current is flowing in the input conducts of theobject, these means advantageously being comprised by coils 17 andmeasuring being done inductively. Suitably the detecting means arearranged so that only loads exceeding a certain value are registered asload, that is power supply. This is to avoid registering the currentflowing to, for example, an oven lamp, a transformer etc. of a stove asload, but only the current that flows to supply hot plates and oven.When the object is a stove, the value preferably is approximately 50watt. Through a conduct 18 these means output signals to the controlunit regarding the power supply to the object.

Furthermore, the device comprises a means 19 which, during a break ofthe power supply to the object, measures the time of this break. Here,break in the power supply is referred to as a load which goes below theload which the detecting means register as load. In the block diagramthis means is represented by the block 19 and is connected to thecontrol unit through the conducts 20, 21, and to the output of thedetecting means through a conduct 22. It is initiated and reset to zerothrough a signal at the conduct 21 from the control unit as the latterhas obtained a signal from the detecting means that confirms that noload is present. As the time of no load, break, exceeds a predeterminedvalue, this means 19 outputs a signal to the control unit 1 indicatingthat this is the case. In the preferred embodiment, at this signal, thecontrol unit is programmed to bring the means 2 for effecting the timeof power supply interruption, here the timer, to once again start fromzero, that is from the beginning, at its down counting of the operationtime.

Accordingly, at a break in the power supply to the object which exceedsa predetermined value as to time, the device comprises means 1, 13, 19for bringing the means 2 for effecting the time at which the powersupply is to be broken to restart its counting from the beginning.

Furthermore, the preferred embodiment of the device comprises means 23which, as the power supply to the object has been interrupted by thedevice, through signalling at the conduct 32 to the control unit andfurther signalling from the latter, bring the means for detectingwhether the object's own breakers are closed or not to execute theirdetection with a time period between the detecting function occasionswhich step-wise becomes longer. In the block diagram shown, these meanscomprise the block 23. When the device has interrupted the power supplyto the object, this means 23, preferably through a signal at the conduct32 to the control unit, controls the breakers of the device, which thenare open, by means of signals to close for short periods with astep-wise longer pause between each respective occasion and thereby makeit possible for the detecting means to determine whether the object'sown breakers are closed. This function is initiated when the breakers 11of the device by any reason, e.g. elapsed operation time, is brought toopen by a signal from the control unit, the control unit giving a signalto this means to start its function through a conduct 24. The functionis interrupted as soon as the detecting means 13 have found the object'sown breakers no longer closed and have given a signal to the controlunit 1 indicating this, and the control unit has forwarded thisinformation to the means 23 by means of a signal on the conduct 33. Themeans 23 for executing this timer function is preferably arranged insuch a way that it effects the maintenance of the time period betweenthe detecting function occasions at a predetermined, maximum value afterthe step-wise increase of the time period to this value. For a stove,the first pause is preferably approximately 1 second, whereafter thelength of the subsequent pauses is step-wise increased by, for example,1 second at a time until a pause period of approximately 1 minute isobtained, and remains thereafter at this value.

The block diagram shown comprises also a unit symbolised by a block 25the principal function of which is to function as an arrangementmonitoring the object. Such a known arrangement does certainly alreadyexist for the monitoring of stoves, and is described in the Swedishpatent SE 8800625-9 (461 560) of the applicant. Signalling is hereaccomplished through conducts between this arrangement and the deviceaccording to the invention. The device according to the inventioncomprises means 1 which, at a given signal from the above arrangement25, sees to that the power supply to the object in question isinterrupted. Here, these means are formed by the control unit which, viaa conduct 26, receives such signals and on the basis thereof outputsignals, via a conduct 27, to the breakers 11 of the device regardinginterruption of the power supply to the object. Simultaneously a controlunit also outputs a signal to the means 23 for creating a step-wiselonger time period between the detecting function occasions to initiateits function.

Such signals from the monitoring arrangement 25 to the device accordingto the invention are preferably output by the arrangement in case ofoverheating of, for example, hot plates and/or forming of flames.

A further signalling taking place between the control unit 1 and themonitoring arrangement 25 refers to the possibility of occasionallydeconnecting the means 2 for effecting the time for interruption of thepower supply to the object, and said counting means 10, the control unitand the monitoring arrangement thereby constituting means for thisfunction. Therefore, the monitoring arrangement is provided with amember for effecting this function which is maneuverable by a user, andwhen the member is maneuvered for such a function a signal istransmitted through a conduct 28 from the monitoring arrangement to thecontrol unit. Suitably the de-connection only applies for one operationperiod, that is continues use of the stove with breaks in the use thatgo below the above mentioned, predetermined time, during which operationperiod the means 2 for effecting the time for interruption of the powersupply to the object is not forced to start its down counting of theoperation time from zero. If the control unit obtains a signal from thedetecting means with reference to a pause which exceeds said time, thelast mentioned means 2 and the counting means 10 will be reconnected.

Furthermore, the device according to the invention comprises a means forsending a signal to the monitoring arrangement which indicates that theobject is supplied with power. Here, this means is constituted by thecontrol unit 1 which, via a conduct 29, outputs a signal to a buzzerarranged in the monitoring arrangement, which buzzer then releases asound to tell that the object now is supplied with energy, that isturned on. Suitably the monitoring arrangement is also arranged with avisual means which, during this signalling, is effected to execute afunction which makes the operator aware of the object being suppliedwith energy. For example, the visual means may consist of a lamp whichis brought to flash at a signal from the device. Suitably, saidarrangement is also equipped with a switch for turning the sound of thebuzzer off.

As the power supply to the object is interrupted, due to an alarm fromsaid arrangement or due to the elapse of the operation time, a signal isgiven from the device to the monitoring arrangement via a conduct 30,whereby the monitoring arrangement, as it receives this signal, turnsthe buzzer and the visual means off. In connection to the subsequent,above described load test, the device, in a preferred embodiment, isalso provided with means, in the shape of the control unit 1, which atthe end of each pause send a signal to the monitoring arrangement whichgives rise to a sound from the buzzer, this sound preferably beingdifferent from the sound which is released by the buzzer in connectionto the turn on of the power supply to the object.

In the preferred embodiment, the device also comprises means formaintaining the device in a power supply interrupting state until apredetermined time has past after its installation or a power supplybreak of the network supplying the object with power. Here, these meanscomprise the control unit which, when the device has been subjected tolack of power supply, is programmed to transmit a signal via a conduct27 indicating that the device's own breakers shall be kept open until apredetermined time has past.

Finally, it should also be mentioned that the device according to thepreferred embodiment is provided with a visual means 31, preferably alight indicator which at a signal via a conduct 34 from the control unitis activated as the device obtains operational voltage after networkvoltage or after installation.

Of course the invention is not in any way restricted to the preferredembodiment described above, but a plurality of possibilities ofmodifications thereof should be obvious for a man skilled in the artwithout the embodiments thereby diverging from the very thought of theinvention. For example, it is not necessary that the device according tothe invention, as is the case in the preferred embodiment, isconstituted by a plurality of discrete components or units in the wayshown. Of course, the same result can be obtained with a system withintegrated components.

The fact that, in the description, the device according to the inventionhas been exemplified such as applied to an electric stove, the powersupply being referred to as current supply, does not mean that thedevice is delimited to application at such objects. Naturally, it canfind use in a plurality of other contexts, and also where the powersupply not necessarily refers to current supply, e.g. at gas stoves.

Furthermore, it shall be particularly noted that the phrase "effect atwhich time the power supply is to be interrupted" does not only refer todetermination of the time for interruption by means of a timer, but thatthe expression should be understood as "control when the power supply isto be interrupted" and whereby this control then can be effected on atotally other basis than a measure of time, e.g. on the basis ofregistered overheating of hot plates or on the basis of certain numberof on and off switches respectively of the object's own breakers.

We claim:
 1. A device for interrupting power supply to an object havinga first breaker, comprising:means to effect at what time the powersupply is to be interrupted, said means comprising a timer, by means ofwhich a desired operation time of the object can be set, means fordetecting whether the first breaker of the object is closed or not, asecond breaker, responsive to said means to effect, to interrupt thepower supply to the object, means, responsive to said means to effect,for keeping the power supply to the object interrupted, after the powersupply having been interrupted by means of the second breaker, until thefirst breaker is opened, and for connecting the power supply to theobject when the first breaker is opened, further comprising means formeasuring, during a break in the power supply to the object, theduration of the power supply interruption and for delivering, only whenthe duration exceeds a predetermined value, a signal to a control unitadapted to, on receipt of this signal, cause the timer to once againrestart counting of the operation time.
 2. A device according to claim1, further comprising a counting means which effects interrupting of thepower supply to the object by the device when the power supply to theobject has been initiated and interrupted a predetermined number oftimes via the first breaker without the timer having been allowed toreach the end of the operation time.
 3. A device according to claim 2,wherein the first breaker are controlled through a thermostat function.4. A device according to claim 1, wherein the counting means isoperatively connected depending on which part of the object is suppliedwith energy.
 5. A device according to claim 1 further comprising meansfor pre-setting the operation time in the timer.
 6. A device accordingto claim 1, further comprising means effecting maintenance of the devicein an energy supply interrupting state until a preset period has elapsedafter installation of the device or after the occurrence of a break inthe power supply of a network providing the device with energy.
 7. Adevice according to claim 1, further comprising means which, at a givensignal from an arrangement monitoring the object and associated to thedevice, effect the interrupting of the power supply to the object.
 8. Adevice according to claim 1, wherein the object is a stove.
 9. A deviceaccording to claim 1, wherein the power supply refers to supply ofcurrent.
 10. A device for interrupting power supply to an object havinga first power supply breaker comprising:means to control when the powersupply is to be interrupted, means for detecting whether the first powersupply breaker of the object is closed or not, a second power supplybreaker for breaking the power supply to the object, means for keeping,after the power supply having been interrupted by means of the secondpower supply breaker, the power supply interrupted until the first powersupply breaker of the object is opened, and for connecting the powersupply to the object when the first power supply breaker is opened,wherein, when the power supply to the object has been interrupted by thedevice, the means for detecting whether the first power supply breakeris closed or not to execute its detecting function with a longer periodbetween detecting function occasions.
 11. A device according to claim10, wherein the said means to control comprises a timer by means ofwhich a desired operation time of the object can be set.
 12. A deviceaccording to claim 10, further comprising means which effect maintenanceof a period between the detecting function occasions at a predeterminedmaximum value after the period having been increased to thepredetermined maximum value.
 13. A device according to claim 10, furthercomprising means which, at a given signal from an arrangement monitoringthe object and associated to the device, effect the interrupting of thepower supply to the object.
 14. A device according to claim 10, whereinthe object is a stove.
 15. A device according to claim 10, wherein thepower supply refers to supply of current.
 16. A device according toclaim 10, wherein the first breaker is controlled through a thermostatfunction.